Lens.



E. D. TILLYER.

LENS.

APPLICATION HLED NOV. 29. I916.

H: Maw

'pleted lens.

UNITED STATES PATENT OFFICE.

EDGAR D. TILLYEB, OF SOUTHBBIFGE, MASSACHUSETTS,

SOUTHBBIDGE, MASSACHUSETTS, A VOLUNTARY ASSO- OPTICAL COMPANY, 0F GIATION OF MASSACHUSETTS.

ASSIGNOB T0 AMERICAN LENS.

Specification of Letters Patent.

Patented May 21, 1915.

Application filed November 29, 1918. serial No. 184,180.

To all whom it may concern.

Be it known that I, Eooan D. Trnnrnn, a citizen of the United. States, residing at Southbrid in the count of Worcester and State of assachusetts, ave invented oer, tain new and useful Improvements in Lenses, of which the following is a specification. v

This invention relates to improvements in lenses and has particular reference to lenses of the bifocal or multifocal type.

One of the leading objects of m present invention is the provision of a nove and improved construction of lens formedfrom two or more parts having difierent indices of refraction, in which the parts shall be very securely and at the same time detachably united.

A further object of the present invention is the provision of an improved construction of two-part lens, in which one .of the parts shall be so formed and adapted that it will to a maximum resist any accidental relative movement of the parts. r

A further object of the invention is the provision of an improved lens and process of producing the same, which will permit of the construction of the lens with a minimum amount of labor and consequently considerably reduce the cost of production of the same. I

Other objects and advanta es of my im- -proved construction should readily apparentby reference to the followmg spec cation takenin connection withthe accoman in drawings formin a part thereof, iind it rill be understood hat I may make any modifications in the specific details of construction shown and described within the scope of the appended claims without de arting from or exceeding the spirit of my mventlon.

Fi re I represents a plan view of a blank for t e construction of my improved lenses. Fig. II represents a similar "view of a com Fig. III re parts of my ens in condition forun'itmg.

Fig. IV re resents an enlarged fragmentaiiy sectiona view of the plarts ig. V represents a sum ar view showing VI represents a corresponding sectiona view through the complete lens.

resents a sectional view of the opaque, but presents Fig. VII represents a sectional view of an alternative form of my construction.

Fig. VIII is a semi-diagrammatic view llustratin the refraction of light through a pond ut unpolished glass surface.

' 1g. IX is a snnilar view showing the surface treated with my filler or cement.

In the drawings, in which similar characters of reference are emplo ed to denote correspondmg parts throng out. the several views, the numeral 1 designatesthe major blank having formed therein the concavity 2 adapted to receive the curved face 3 of the segment 4, this being a well known ty e of construction known as countersunk bi ocal, in which the major ortion 1 and segment 4 are of glass of di erent indices' of refraction so that in the completed lens as illustrated in Fig. VI, the lens may be formed on the segment bearin surface with a contlIHJOllS curve and at t e sametime the two desired foci secured in the lens. It is to be understood, of course, that while I have here articularly described'and illustrated a biocal lens, that the princi he of my invention are equally ap licab e to any form of multifocal, and I, t erefore, do not wish to be specifically limited to the use of my imof a translucent but not transparent member having a whitish surface, the transparency or opaqueness of this surface dependin largely on the grade of abrasive employs in that the coarser the abrasive, the more opaque the surface, while the finer the abrasive, thebetter the surface till the use of the finest abrasive, as mentioned, constitutes what is commonly known as polishing, that is producing the absolutely transparent optically correct surface regularly employed with lenses.

It is-not understood 1) many, however that this ground glass sur ace is not of itself the appearance of opacity or translucency, but not transparency only on account of the fact that the surface is rough, as particularly illustrated in theenlar ed view, Fig. IV, comprisin the points or ills 5, as they may be tel-meg and the corresponding hollows or indentations 6, between the points. This formation produces in effect a series of irregular teeth or substantially prism members, each of which bends or refracts the light rays seeking to pass through the ground glass surface so that the result is the rays are so bent or refracted that no image is transmitted by them but only the effect on the eye produced of the matte or ground surface, although every point individually considered is entirely transparent or transmissive of image bearing light rays.

t is, therefore, the PUIPOSB of my present invention to make use 0 this optical principle in connections with the formation of bifocal or multifocal lenses, or the uniting of two glass surfaces.

In the utilization of this idea as illustrated in Figs. I to VI of my patent drawings inelusive, I suitably'form the major blank 1 and have then roughly ground in it the concavity 2, but have omitted the polishing of the countersink, which has hitherto always been deemed necessary, thus leavin the blank as clearly illustrated in Fig. I ,with the series of points or hills 5 projectin in the concavity portion. I then suitably orm the segment 4 with the pro erly curved and polished surface3, adapte to fit into the concavity 2.

The parts bein thus formed itrwill be understood by re erence to Fig. IV for example, that when the segment 4 is placed in position in the concavity the oint 5 will project into engagement therewith and will tend to exert a frictional or biting effect with reference thereto to prevent sliding movement of the segment within the concavity.

To unitethe partsI then employ a suitable o pti'cal cement having substantially the same index of refraction as the major blank. For example, if desired the ma or blank ma be made of glass having an index 1.523 while the segment is formed from glass having an index of 1.62. In uniting the parts I may then emplo among other cements or mediums the wel known Canada balsam, having the refractive index 1.53, or substantially that of the ma'or blank. In the uniting of the parts the alsam is placed within the concavlty in the usual manner and in suitably heated or softened condition so that it will flow between the hills or points 5 and fill up all of the hollows 6 to produce a smooth and continuous surface to the concavity, whose curvature is' determined by the points 5 under ordinary conditions, or which may be varied within reasonable limits by suitable molding or forming of the-cement or medium 7 which is engaged with the points.

It will be understood that if desired, as for temporary trial wear or the like, an optical surface may be formed with the ground portion of the blank 1 as a base, and the actual curvature produced or finish of the curve, formed by this shaping of the medium 7 in place of the final polisliing of the surface, and that an optically usable lens is thus provided which is capable of entirely satisfactory use up to a point when the surface, on account of its softness, would be impaired by scratching or the like, this being the only limit to the optical usability of a lens surface so constructed, and being the only reason that I have specified this surface as adapted especially only for temporary or trial purposes.

In the construction of a bifocal, however, this is eminently satisfactory due to the fact that the countersink being filled with the cement or filler medium 7, the segment 3 is then placed in position while the cement is still in a soft or heated condition,

and the segment pressed firmly into place, the medium 7 taking care of the difference. if any, between the curve of the polished surface 3 of the segment 4 and the curve of the countersink 2, interlockin with the points or teeth 5, fillin up all t e hollows and at the same time %rmly engaging the polished surface 3 of the segment to firmly retain the segment in position. It will be understood that while the medium 7 serves to secure the countersink that at the same time the countersink is in contact with the points 5 which have a frictional or bitin effect on the polish of the se ent and serve to prevent any sli ping o the same.

It is to be understoo that for the successful and satisfactory construction of my lens, it .is' absolutely essential that the re fractive index of the substance 7 be substantially that of the ground but unpolished surface to. which it is applied, in that the optical effect produced is substantially that o completion of the ground surface, in that the medium 7 fills u the hollows, making an even surface wit the points 5 or as molded so that the various light rays in place of being deflected in varying directions, as indicated in the diagrammatic view in Fig. VIII, which illustrates the effect reduced by light waves emerging through the ground glass surface on account 50f the prism present, ass straight through the ground glass sur ace and filler 7 due to their corresponding index of refraction, as is clearly illustrated in Fig. IX.

From the foregoing description taken in connection with the accompanying drawings, the construction and advantages of my improved lens or bifocal lens should be readily apparent. and it will be seen that I have provided an improved construction in which it is unnecessary to polish the surface of the lens, in that the effect of the surface polished, namely the elimination of noticable hills and hollows, is produced by the filling up of these hollows to secure a smooth or polished effect surface through the medium of a filler or cement of the same refractive index as the glass to which it is applied, and it will be further noted that my improvement is particularly adaptable for use in connection with the construction of bifocal lenses, both on account of the fact that the segment of the bifocal lens serves as a cover plate to protect the tiller 7 and prevent injury to the artificial surface thus produced to which on account of its relative softness, it might be subject in the absence of a cover plate, and also on account of the fact that the roughened ground but unpolished surface will provide points or hills coming just to the surface of the filler 7, but being disposed sufficiently at the surface of the filler or cementing medium to have a frictional or biting engagement with the segment, tending to resist any relative slipping movement of the segment and major blank either during the final grindin operation in the production of the finishe lens 6, or subsequently when the finished lens 6 is in use.

It will further be understood that while I have primarily described in the specifica tion the polished surface 3 as being on the segment and the unpolished surface being on the countersink, that the parts may be reversed and the countersink polished and the surface of the se ment left unpolished,

as indicated in Fig. V I, it being understood that in this event it is necessary to employ a cement or filler medium of the same refractive index as the segment in place of the refractive index of the major blank, it being essential to my im rovement that the refractive index of the ller correspond to the refractive index of the member having the unpolished surface, so that the effect of the light rays will be as indicated in Fig. IX and that no deflection will take place as would be the case were the filler an unpolished surface formed from material having different indices of refraction.

I claim:

1. A bifocal lens, including a major blank and a segment, one of said parts having projecting points engaging the other to resist relative slipping of the parts.

2. A bifocal lens, including a major blank and a segment, one of said parts having projecting points engaging the other to resist relative slippin of the parts, and a filler of the same re ractive index as the major blank adapted to fill up the hollows caused by grinding to produce a smooth surface.

' 3. A two part optical lens, in which one of the parts has a roughened surface for engagement with the other part, and an interposed filler cement of the same refractive index as the roughened part for securing the parts in engagement.

4. An optical lens includin a major blank and a segment, one of sai parts having a roughened surface engaging the other to resist relative slipping of the parts.

In testimony whereof I afiix my signature in the presence of two witnesses.

EDGAR D. TILLYER.

Witnesses:

H. K. PARSONS, H. H. STYLL. 

